This invention relates to thermoformed, heat-resistant, foamed, crystalline plastic materials which are particularly useful as light weight, ovenable food containers.
The Siggel et al U.S. Pat. No. 3,470,114 the entire disclosure of which is expressly incorporated herein by reference, describes the formation of amorphous, foamed plastics which may be shaped by various techniques such as injection molding. These plastics are essentially composed of the reaction product of a polyester with a polycarbonate. However, objects formed from this material tend to deform at elevated temperatures due to the amorphous nature of the plastic.
The Dempsey et al U.S. Pat. No. 4,127,631, the entire disclosure of which is also expressly incorporated herein by reference, describes a non-foamed, thermoformed polyester sheet material. However, as compared with foamed polyester, this non-foamed material has a relatively high density.